GURPS?

Currently, as I’m on something of a science fiction trip, I’m considering attempting to adapt the D20 system for a futuristic setting. Perhaps I might even attempt a Mass Effect D20 game. Also in the works is the possibility of a steampunk game- steampunk is something I’ve been fascinated in for a long while now, and the idea of running a game in a steampunk setting greatly appeals to me. The question, however, is whether or not the D20 system is suited for either game. Certainly, I can houserule my way through both. As well, there are likely sourcebooks which include instructions for making games with such settings.

Ultimately, however, the D20 system has but on primary limitation: it is designed chiefly for fantasy games. Most of the sourcebooks pertain to this, the majority of the rules are geared towards a high fantasy/medieval setting. As such, the system may have to be heavily tweaked before being utilized for the setting. You see, I am something of a completionist when it comes to design. I have specific standards which must be met; if they are not, I am unsatisfied with my progress and hence unable to comfortably run a game.

I’m not one hundred percent certain what system the default science fiction ruleset (beyond D20, that is) utilizes. However, I do know that there is a rather complete GURPS ruleset designed for a steampunk game-though this would involve learning a new system. I’m not necessarily opposed to that, but I’m also uncertain if GURPS will provide the roleplaying experience I am looking for. I have heard good things about it: that it has rules specifically designed to forward a game’s narrative, that it’s much more story-oriented, much simpler, et-cetera. I shall certainly give the sourcebooks a read, at which point I will throw together a comparison of the two, with my notion of which would better suit my purposes; including the strengths and weaknesses of both.